UNIVERSITY  OF 

ILLINOIS  LIBRARY 

AT  URBANA-CHAMPAIGN 

ACES 


NOTICE:  Return  or  renew  all  Library  Materials!  The  Minimum  Fee  for 
each  Lost  Book  is  $50.00. 

The  person  charging  this  material  is  responsible  for 
its  remrn  to  the  library  from  which  it  was  w.thdrawn 
on  or  before  the  Latest  Date  stamped  below. 


Then,  mutilation,  and  underlining  of  book  •"£ 

nary  action  and  may  result  in  d.sm.ssal  from  the  Un.vers.ty- 

To  renew  call  Telephone  Center,  333-8400 


UNIVERSITY    OF    ILLINOIS    LIBRARY    AT    URBANA-CHAMPAIGN 


L161— O-1096 


JUN  1  6  2005 


UNiVERSJTYOFJUINOI 


UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station, 


URBANA,  NOVEMBER,  1903. 


BULLETIN    No.   89. 


NOTES  ON  THE  INSECTICIDE  USE  OF 
THE  GASOLINE  BLAST  LAMP 


BY  S.  A.  FORBES,  STATE  ENTOMOLOGIST. 

The  use  of  the  ordinary  plumber's  torch,  or  some  modification  of  it, 
for  the  destruction  of  injurious  insects  on  their  food  plants  seems  to 
have  occurred  independently  to  several  persons  during  the  last  few 
years,  and  to  have  been  tried  with  some  care  as  a  practical  measure  by 
several  disinterested  men  competent  to  make  exact  observations  and  to 
report  results  without  bias  or  prejudice. 

Mr.  S.  A.  McHenry,  recently  superintendent  of  one  of  the  horticul- 
tural substations  of  the  Texas  Agricultural  Experiment  Station,  is  re- 
ported to  have  used  it  for  several  years  against  the  harlequin  cabbage- 
bug,  and  Professor  J.  M.  Stedman,  of  the  Missouri  Experiment  Station, 
has  also  used  it  against  the  same  insect.  Professor  E.  H.  Pettit,  of  the 
Michigan  Agricultural  College,  tried  it  on  the  San  Jose  scale  as  far  back 
as  1897,  publishing  in  the  Bulletin  of  the  Michigan  Experiment  Station 
the  earliest  report  of  an  exact  experiment  with  it  which  I  have  seen ;  and 
Professor  Carig,  o'f  the  Horticultural  Department  of  Cornell  University, 
has  also  tried  it  on  this  scale.  Professor  E.  Dwight  Sanderson,  of  the 
Texas  Agricultural  College  and  Experiment  Station,  has  used  a  form  of 
it  on  the  cotton  boll-weevil.  Professor  Thomas  B.  Symons,  of  the  Mary- 

145 


146  BULLETIN  NO.  89.  [November, 

land  Agricultural  College  and  Experiment  Station,  used  it  experiment- 
ally on  the  San  Jose  scale,  and  on  beetles  infesting  the  aster.  Professor 
J.  L.  Phillips,  State  Entomologist  of  Virginia,  has  also  tested  it  on  the 
San  Jose  scale  with  unusual  thoroughness ;  Professor  F.  M.  Wehster,  En- 
tomologist of  the  Ohio  Agricultural  Experiment  Station,  had  it  tried 
four  years  ago  by  an  assistant,  Mr.  C.  W.  Mally  (now  Government  Ento- 
mologist in  Cape  Colony,  South  Africa),  on  a  variety  of  insects,  includ- 
ing the  chinch-bug;  and  two  of  my  own  assistants,  Mr.  E.  S.  G.  Titus 
and  Mr.  G.  I.  Eeeves,  have  used  it  on  scale  insects,  caterpillars,  and 
moths,  have  tested  it  for  the  destruction  of  fungus  parasites  of  the 
green  leaf,  and  have  determined  its  effects  on  various  kinds  of  vegetation 
when  applied  in  a  way  to  kill  the  insect  enemies  of  the  plant.  Most  of 
these  experiments  are  unpublished,  but  their  results  have  been  gener- 
ously placed  at  my  disposal  for  use  in  this  brief  discussion. 

Although  no  one  of  those  here  mentioned  has  made  a  trial  of  the 
gasoline  torch  for  all  the  insecticide  and  fungicide  purposes  which  it 
might  possibly  serve,  the  total  results  have  a  considerable  value  as  show- 
ing definitely  some  things  which  can  and  some  things  which  can  not  be 
done  with  it,  and  as  indicating  the  directions  in  which  further  trials 
may  be  made  if,  indeed,  it  appears  that  further  trial  is  necessary  or 
worth  while.  Some  variation  and  conflict  in  the  reports  of  some  of 
these  experiments  are  evidently  due  to  differences  in  the  apparatus  used, 
this  varying  from  a  poorly  constructed  and  feeble  torch,  made  in  Illinois 
especially  for  insecticide  work,  to  a  large  and  powerful  blast-lamp,  used 
in  Texas  for  burning  the  thorns  off  prickly-pears. 

The  idea  that  exposed  insects  of  small  size  may  be  quickly  destroyed 
by  the  sudden  and  brief  application  of  a  blast  of  very  hot  air,  or  even 
of  actual  flame,  without  injury  to  the  plant  on  which  they  may  be  feed- 
ing at  the  time,  strikes  one  favorably  at  first  thought;  and  there  seems, 
in  advance,  to  be  no  obvious  reason  why  this  method  may  not  have  a 
considerable  practical  value.  The  living  animal  is  often  more  sensitive 
to  sudden  heat  exposures  than  the  living  plant,  and  the  margin  between 
exposures  fatal  to  each  may,  in  some  cases,  be  so  wide  as  to  make  this 
method  fairly  safe  in  ordinary  practice.  The  smaller  the  insect,  of  course 
the  more  quickly  it  may  be  killed  by  the  hot  blast;  and  the  better  the 
living  tissue  of  the  plant  is  protected  by  a  lifeless  cuticle  or  a  layer 
of  bark,  the  longer  it  may  be  exposed  to  this  blast  without  being  heated 
to  the  point  of  injury.  Bark-lice  on  trees  and  shrubs  are  thus  favor- 
able objects  for  experiment;  but  where  thick-bodied  insects,  like  cater- 
pillars and  large  beetles  or  bugs,  themselves  covered  with  a  dense  crust 
of  lifeless  cuticle,  are  feeding  on  the  young  green  leaf,  the  margin  of 
safety  is  greatly  narrowed  and  may  wholly  disappear.  The  practical 
utility  of  this  method  of  destroying  insects  in  any  case,  evidently  de- 
pends on  the  existence  and  extent  of  this  margin  of  safety. 


1903]  INSECTICIDE    USE    OF   THE    GASOLINE    BLAST  LAMP.  147 

The  gasoline  blast  may,  in  fact,  be  used  to  kill  any  insect  on  any 
plant.  The  time  and  method  of  use  necessary  to  kill  the  insect  will 
vary  widely  for  different  kinds  of  insects  and  for  the  different  states 
and  stages  of  each  kind;  and  the  time  and  method  of  use  sufficient  to 
injure  various  kinds  of  plants  will  likewise  differ  widely  according  to  the 
kinds  and  condition  of  the  plants  themselves.  The  actual  effect  of  the 
blast  on  either  insect  or  plant  will  also  vary  enormously  according  to 
small  details  of  the  method  by  which  it  is  applied.  They  will  vary,  first, 
with  variations  in  the  pressure,  which  determines  the  extent  and  heat 
of  the  flame;  second,  with  the  distance  from  the  object  at  which  the  torch 
is  held;  third,  with  the  rate  of  movement  at  which  the  flame  is  passed 
over  the  surface  treated;  fourth,  with  the  temperature  at  the  time  and 
the  amount  and  direction  of  the  wind;  fifth,  with  the  direction  of  the 
blast,  whether  perpendicular  or  oblique  to  the  surface;  and  sixth  (not 
to  specify  further),  with  the  steadiness  with  which  the  flame  is  applied 
to  a  given  surface,  whether  held  at  one  point  for  a  definite  time  or 
swayed  back  and  forth  over  a  considerable  surface  for  a  variable  num- 
ber of  times. 

To  determine  the  effect  of  all  these  different  classes  of  variations 
with  sufficient  exactness  for  practical  guidance,  and  then  to  combine 
all  the  various  results  of  this  inquiry  with  each  other  in  a  way  to  form 
a  system  of  practice  which  can  be  accurately  described  and  safely  recom- 
mended for  general  use,  is  a  task  which  no  intelligent  investigator  would 
enter  upon  lightly,  or  without  such  preliminary  tests  as  would  enable 
him  to  judge  whether  any  important  result  was  likely  to  come  from 
more  exact  and  extensive  experiments.  The  observations  here  reported 
are  all  in  the  nature  of  such  preliminary  tests,  made  by  different  persons, 
each  for  his  own  satisfaction,  on  different  objects,  and  in  different  parts 
of  the  country.  They  are  practical  tests  rather  than  complete  scientific 
experiments,  and  their  value  is  hence  suggestive  rather  than  final.  Those 
which  have  to  do  with  the  San  Jose  scale,  the  harlequin  cabbage-bug, 
and  the  cotton  boll-weevil  are  perhaps  of  the  greatest  interest,  and  will  be 
given  first. 

THE  SAN  JOSE  SCALE. — In  the  fall  of  1897,  Professor  Pettit,  of 
Michigan,  had  five  parallel  burners  fitted  to  an  ordinary  plumber's  blast 
lamp  in  such  a  way  that  a  flame  about  ten  inches  wide  could  be  directed 
against  the  surface  of  a  tree,  and  several  trials  of  this  apparatus  were 
made  during  the  following  winter  on  peach-  and  pear-trees  badly  infested 
with  the  San  Jose  scale.  "The  heat  produced  by  this  lamp,"  he  says, 
"is  very  intense,  and  great  care  must  be  observed  not  to  allow  the 
flame  to  remain  at  any  one  point  long  enough  to  injure  the  tree.  The 
best  results  were  obtained  when  the  flame  was  steadily  moved  so  that 
it  covered  a  space  of  a  yard  in  length  in  from  five  to  ten  seconds.  The 
results  seemed  to  show  that  the  blast  will  kill  the  scale-insects  with 


148  BULLETIN  NO.  89.  [November, 

little  or  no  injury  to  the  tree.  The  trees  were  scorched  in  places  where 
the  flame  had  moved  too  slowly,  and  the  care  necessary  to  avoid  the 
scorching  appears  to  be  the  most  serious  drawback  to  the  use  of  the 
blast  lamp.  In  careless  hands  much  injury  may  be  done  in  a  very  short 
time,  while  the  skillful  handling  necessary  for  success  would  be  rather 
expensive  under  ordinary  circumstances.  Good  judgment  must  be  exer- 
cised always,  and  the  rapidity  and  effectiveness  of  the  work  will  be  much 
modified  by  the  temperature  of  the  air,  the  direction  and  force  of  the 
wind,  the  age  of  the  trees  and  the  thickness  of  the  incrusting  scales." 
Eeferring  to  these  statements  in  a  recent  letter,  Professor  Pettit  writes 
that  he  intended  that  the  lamp  should  be  used  only  in  connection  with  a 
spray  for  burning  off  or  loosening  the  outer  layers  of  a  crust  of  scales 
so  that  a  fluid  insecticide  might  penetrate  to  those  beneath.  "I  now 
realize,"  he  says,  "that  the  same  effects  may  be  obtained  much  more 
cheaply  in  other  ways/' 

By  Professor  Craig,  of  Cornell  University,  a  torch  much  advertised 
for  the  destruction  of  insects  was  used,  May  19,  1903,  against  the  San 
Jose  scale  on  the  apple,  medlar,  buffalo-berry,  and  dogwood.  Different 
branches  were  flamed  in  various  ways  to  ascertain  the  time  necessary 
to  kill  the  scale  and  to  determine  the  minimum  exposure  to  the  flame 
of  the  torch  which  would  kill  the  cambium  layer  of  the  tree  or  shrub. 
In  respect  to  time  of  exposure  three  methods  of  treatment  were  used: 
passing  the  flame  so  rapidly  over  the  surface  that  it  merely  touched  each 
point  for  an  instant;  moving  it  at  the  rate  of  one  foot  per  second;  and 
holding  it  stationary  on  the  infested  spot  long  enough  to  count  one. 
The  scales  were  reported  to  have  been  killed  in  every  case  save  one,  in 
which  a  twig  of  dogwood  had  been  very  rapidly  flamed.  "The  general 
results,"  writes  Professor  Slingerland,  "were  summarized  as  follows: 
First,  the  torch  is  impracticable  for  large  trees  of  apple,  plum,  pear, 
peach,  or  cherry,  because  of  the  amount  of  time  required  to  flame  the 
whole  tree.  It  would  take  a  man  several  hours  thus  to  go  over  one 
large  tree;  second,  there  is  great  danger  of  injuring  buds  or  the  cambium 
layer  on  thin-barked  trees;  third,  the  torch  might  be  used  on  small 
nursery  stock  or  ornamental  shrubs  by  an  experienced  operator  who 
knew  exactly  what  time  to  expose  the  plant  to  the  flame." 

Professor  Phillips,  of  Virginia,  made  use,  against  the  San  Jose  scale, 
in  1903,  of  a  torch  sent  by  the  manufacturing  company  for  trial  to  Pro- 
fessor Alwood,  of  that  state.  "March  28  of  this  year,"  he  says,  "I  used 
this  gasoline  torch  on  two  apple-trees  four  years  of  age.  These  trees 
were  moderately  infested  with  the  San  Jose  scale,  and  were  treated  by 
running  the  torch  over  the  surface  several  times.  One  tree  was  exposed 
to  the  torch  about  twice  as  long  as  the  other.  This  treatment  did  not 
appear  to  injure  the  trees,  neither  did  it  kill  a  perceptible  number  of 
insects. 


1903]  INSECTICIDE    USE    OF   THE    GASOLINE    BLAST   LAMP.  149 

"I  was  not  satisfied  with  this  trial,  however,  and  detailed  a  student 
assistant,  Mr.  E.  F.  Cole,  to  test  the  torch,  which  he  did  August  7.  The 
tree  treated  was  a  four-year-old  apple,  badly  crusted  with  the  San  Jose 
scale.  As  it  would  he  entirely  impracticable  to  use  this  torch  against 
the  San  Jose  scale  during  the  summer,  this  treatment  was  confined  al- 
most entirely  to  the  trunks  and  main  branches  of  this  tree,  but  in 
treating  the  tree  in  this  manner,  of  course  a  few  of  the  leaves  were  also 
reached  by  the  flame.  The  treatment  was  so  severe  that  the  leaves  on 
the  treated  portions  of  the  tree  were  killed  at  once,  and  when  examined 
en  August  20,  portions  of  the  bast  tissues  of  the  bark  were  found  injured 
also.  Quite  a  large  number  of  scale  insects  were  alive  at  that  date. 

"Judging  from  these  two  tests,  I  consider  that  the  use  of  this  torch 
is  quite  tedious  and  impracticable,  even  on  small  trees.  Besides,  such  a 
small  per  cent,  of  the  San  Jose  scales  were  destroyed  by  it,  even  where 
the  trees  were  seriously  injured  by  its  use,  that  I  do  not  consider  it  a 
practicable  remedy." 

Professor  Symons,  of  Maryland,  writes  me  that  he  personally  con- 
ducted some  experiments  with  the  same  kind  of  a  torch  on  different 
varieties  of  peach  and  plum  infested  by  the  San  Jose  scale,  but  that  the 
results  were  not  at  all  satisfactory.  Although  the  insects  were  dead  two 
weeks  later  on  the  parts  which  had  been  hit  by  the  flame,  young  scales 
were  crawling  about  over  the  surface  in  considerable  numbers,  showing 
that  it  had  been  impossible  to  reach  all  parts  of  the  tree,  especially  at 
the  ends  of  the  branches.  If  used  when  the  tree  was  in  leaf  he  could 
not  avoid  burning  the  foliage.  As  a  result  of  his  experiments,  Professor 
Symons  concludes  that  it  is  impracticable  to  control  the  San  Jose  scale 
with  this  torch. 

To  these  observations  by  experts  I  may  add  a  note  of  a  trial  of  the 
torch  made  by  a  practical  gardener,  on  some  infested  trees  belonging 
to  J.  W.  Stanton,  of  Kichview,  in  this  state.  By  oversight,  these  trees 
were  sprayed  with  whale-oil  soap  before  they  had  been  critically  exam- 
ined as  to  the  final  effects  of  the  blast  on  the  San  Jose  scale;  but  Mr. 
Stanton  Avrites  me  that  from  what  he  could  see  of  the  effects  of  the 
treatment  at  the  time,  he  is  of  the  opinion  that  it  would  not  be  successful 
on  tree  fruits.  One  of  my  horticultural  inspectors,  Mr.  K.  W.  Braucher, 
happened,  however,  to  examine  one  of  these  trees  after  the  treatment 
with  the  torch  and  before  the  application  of  the  whale-oil  soap,  and 
found  that  the  bark  was  scorched  in  some  places,  and  that  in  others 
the  scales  were  still  alive. 

From  the  foregoing  experiments,  it  is  clear  that  the  gasoline  torch 
has  at  best  only  a  very  limited  application  in  the  treatment  of  trees 
infested  by  the  San  Jose  scale.  It  might  be  occasionally  used  to  advan- 
tage, as  suggested  by  Professor  Pettit,  to  burn  off  the  outer  part  of  an  un- 
usually thick  crust  of  scales  on  the  trunk  and  largest  branches  of  a  tree, 


150  BULLETIN  NO.  89.  [November, 

preliminary  to  a  treatment  with  the  lime-and-sulphur  wash.  As  this 
insecticide  does  not  penetrate  readily  to  any  great  depth,  it  is  sometimes 
necessary  to  repeat  a  spraying  after  a  time  if  the  tree  is  too  thickly 
incrusted.  This  second  spraying  might  perhaps  be  omitted  if  the  torch 
were  first  used  on  the  crust  of  scales.  It  would  be  the  merest  folly,  how- 
ever, to  think  of  using  it  as  a  substitute  for  an  insecticide  spray  in  the 
treatment  of  the  San  Jose  scale,  or  for  any  general  treatment  of  orchard 
trees  for  any  purpose  whatever. 

This  torch  was  also  tried  on  certain  other  orchard  scales  at  Urbana 
during  the  fall  of  1902,  but  for  reasons  to  be  given  presently  these  tests 
are  reported  separately  farther  on. 

THE  HARLEQUIN  CABBAGE-BUG. — The  introduction  of  the  use  of  the 
gasoline  torch  against  the  harlequin  cabbage-bug  in  the  South  seems 
to  be  due  to  Mr.  S.  A.  McHenry,  recently  superintendent  of  one  of 
the  substations  of  the  Texas  Agricultural  Experiment  Station.  Indeed, 
Professor  Sanderson,  official  Entomologist  of  that  state,  writes  me  that 
so  far  as  he  knows,  Mr.  McHenry  was  the  first  man  to  make  practical 
use  of  the  blast  torch  against  insects  of  any  kind.  He  is  said  to  have 
used  it  successfully  for  several  years,  as  have  others  in  his  section  of 
the  state,  but  of  late  he  has  made  comparatively  little  use  of  it  for  that 
purpose  because  of  the  amount  of  work  required  to  go  over  a  cabbage 
plant  with  the  torch. 

Professor  J.  M.  Stedman,  of  Missouri,  writes  more  confidently  of 
its  usefulness  against  the  cabbage-bug,  saying,  under  date  of  October 
28,  1903,  "I  have  not  found  the  gasoline  torch  of  any  special  value  as  an 
insecticide  apparatus  except  in  extreme  cases  when  one  has  a  sufficient 
number  of  the  harlequin  cabbage-bugs  in  his  cabbages  to  cause  serious 
trouble.  I  have  then  used  this  torch  to  good  advantage.  One  can  very 
readily  pass  over  the  cabbages  fast  enough  not  to  injure  them,  find  at  the 
same  time  to  kill  the  harlequin  bugs.  It  is  not  necessary  to  have  the  bugs 
scorched  sufficiently  to  drop  at  once,  as  I  have  found  that  they  will  ulti- 
mately die  if  this  intense  heat  has  been  very  rapidly  applied/' 

This  cabbage-bug  is  not  widely  destructive  in  this  state,  although 
it  is  continuously  present  in  some  parts  of  southern  Illinois,  and  during 
one  season  extended  its  injuries  as  far  north  as  Champaign,  and  was 
once  found  in  Chicago  by  Mr.  A.  Bolter.  The  reported  effectiveness 
of  this  torch  against  this  insect  suggests  the  trial  of  it  against  other 
bugs,  which  cannot  be  killed  with  arsenical  poisons  since  they  do  not 
eat  the  solid  substance  of  their  food  plant  but  merely  suck  its  sap. 

THE  COTTON  BOLL-WEEVIL. — The  appearance  in  Texas  of  the  snout- 
beetle  known  as  the  Mexican  boll-weevil  has  caused  general  and  justi- 
fiable alarm  among  the  cotton-growers  of  the  South,  and  the  Texas 
State  Entomologist,  Professor  Sanderson,  has  devoted  himself  to  an 
assiduous  study  of  the  insect  and  has  made  many  experiments  for  its 


1903]      INSECTICIDE  USE  OF  THE  GASOLINE  BLAST  LAMP.        151 

destruction  and  control.  This  is,  indeed,  the  most  important,  pressing, 
and  perplexing  problem  which  the  economic  entomologist  now  has  to 
deal  with  in  the  Southern  States.  In  the  course  of  his  work  against  this 
insect  Professor  Sanderson  has  tried  two  forms  of  the  gasoline  torch; 
one,  a.  hlast-lamp  known  as  the  pear-burner,  used  in  southwestern  Texas 
for  burning  the  thorns  off  the  prickly-pear,  and  the  other  a  torch  sent 
him  from  Illinois  by  a  dealer  who  offers  and  advertises  it  for  sale  for  the 
destruction  of  insects.  The  latter  was  found  so  faulty  in  construction 
that  it  could  not  be  used,  and  it  was  consequently  returned. 

The  pear-burner,  which  generates  a  much  more  powerful  blast  than 
any  of  the  smaller  torches,  was  tried  by  Professor  Sanderson  for  burning 
up  the  squares  of  the  boll-weevil  as  they  lay  upon  the  ground,  but  so  far, 
as  he  writes  me  October  28  of  this  year,  he  has  not  had  sufficient  suc- 
cess with  it  to  indicate  that  it  has  any  value  for  this  purpose. 

The  only  other  beetles  on  which  it  has  been  tested  by  any  of  my 
correspondents  are  certain  unspecified  species  found  on  aster  by  Pro- 
fessor Symons,  of  Maryland.  "In  this  case,"  he  says,  "it  was  effective 
in  killing  the  beetles,  but  one  has  to  be  so  extremely  careful  not  to  hurt 
the  flowers  that  I  would  hardly  recommend  it  for  practical  use." 

EXPERIMENTS  AT  URBANA. — In  response  to  my  request,  made  August 
o,  1902,  to  the  inventor  and  patentee  of  a  modified  form  of  the  gasoline 
torch  intended  especially  for  insecticide  work,  one  of  his  instruments 
was  sent  me  with  directions  for  its  use,  and  was  at  once  put  into  the 
hands  of  my  most  experienced  field  assistant,  Mr.  E.  S.  G.  Titus  (now 
assistant  to  the  United  States  Entomologist),  who,  with  the  aid  of  an- 
other assistant,  Mr.  George  I.  Beeves  (now  an  assistant  in  the  Entomo- 
Jogical  Department  of  the  University  of  Missouri),  tried  it  at  various  times 
during  the  following  two  months  on  such  kinds  of  injurious  insects  as 
could  be  found  in  any  number  at  Urbana  at  that  time  of  the  year.  It 
was  further  tried  on  a  fungus  parasite  of  the  lilac  leaf,  and  on  various 
kinds  of  vegetation  to  determine  the  effect  on  the  plants  of  an  exposure 
sufficient  to  kill  the  insects  infesting  them.  Although  sent  me  expressly 
for  experimental  purposes,  this  instrument  proved  to  be  relatively  so 
weak  in  action  that  its  use  by  us  should  probably  be  regarded  as  a  test 
of  the  value  of  this  kind  of  a  torch  rather  than  that  of  the  torch  method 
in  general ;  and  it  is  on  this  account  that  I  have  kept  our  own  statements 
separate  from  those  made  to  me  by  others,  most  of  whom  seem  to  have 
worked  with  a  more  efficient  apparatus. 

The  results  of  our  various  trials  are  here  given  as  reported  to  me  by 
Mr.  Titus  at  the  close  of  his  series  of  experiments,  about  October  20. 

"The  torch  is  simply  an  ordinary  "plumber's  torch"  fitted  with  a  two- 
gallon  gasoline  tank  and  a  three-foot  piece  of  rubber  tubing.  A  short 
iron  discharge  pipe  connects  the  rubber  tubing  with  the  torch. 

"Filled  the  tank  about  half  full  of  gasoline  according  to  directions. 


152  BULLETIN  NO.  89.  [November, 

The  valve  in  this  pump  was  of  leather  and  by  no  means  circular  in  out- 
line, and  it  was  at  first  rather  hard  to  secure  even  pumping  pressure. 
The  connections  were  all  very  dry  and  needed  soaking.  After  an  hour 
or  so  of  work,  cleaning  the  discharge  pipe  and  burner,  we  were  able  to 
light  the  latter  and  get  a  flame. 

"Under  the  heaviest  pressure  obtainable — sufficient  to  force  air 
bubbles  from  the  pump  valve  and  at  the  cut-off  in  the  base  of  the  pump 
— the  flame  was  tried  at  varying  distances.  At  fifteen  inches  from  the 
burner  the  heat  was  scarcely  sufficient  to  singe  the  hair  from  the  hand, 
but  a  little  closer,  ten  to  twelve  inches  distant,  it  would  singe.  The 
burner  was  used  when  running  at  full  force.  The  effects  were  about  as 
follows,  examinations  being  made  at  several  days'  interval. 

"The  trunk  and  smaller  limbs  of  an  apple-tree  were  thoroughly  treat- 
ed. This  tree  was  badly  infested  with  Forbes  and  scurfy  scales,  and  also 
had  on  it  considerable  woolly  aphis.  The  last  mentioned  insects  were 
killed  where  they  were  completely  burned  off  the  limb;  but  where  only 
the  woolly  covering  was  burned  off  and  the  insect  not  actually  caused  to 
drop,  there  was  little  apparent  injury.  The  Forbes  scale  appears  not  to 
have  been  injured,  except  the  young  not  yet  old  enough  to  form  a  scale. 
The  scurfy  scale  was  not  injured.  The  smaller  limbs  were  sufficiently 
treated  to  cause  the  bark  to  blister  in  spots,  without  having  any  appar- 
ent effect  on  mature  scales  of  either  kind. 

"I  have  tried  the  burner  under  ordinary  pressure  at  different  times 
against  various  other  insects  and  foliage.  A  colony  of  fall  web-worms 
in  a  box-elder  tree  was  treated,  and  a  number  of  worms  that  fell  were 
placed  in  a  cage  in  the  insectary.  These  were  given  plenty  of  fresh 
food,  and  did  not  appear  to  be  inconvenienced  by  the  lack  of  hairs  on 
their  bodies.  They  grew,  and  some  of  them  pupated.  Most  of  the 
remainder  were  parasitized,  and  the  few  that  died  were  full  grown  at 
death.  The  parasites  emerged  in  due  time  and  were  preserved. 

"Arctian  caterpillars  (woolly  bears)  treated  to  the  full  force  of  the 
burner  for  ten  to  fifteen  seconds,  or  even  longer,  had  the  hair  thor- 
oughly singed  from  their  bodies,  and  some  were  blistered.  The  majority 
of  these  finished  their  growth  and  pupated.  I  could  see  no  greater 
mortality  among  them  than  ordinarily  occurs  with  this  species  under 
insectary  conditions.  Several  cabbage-worms  were  treated  until  they 
rolled  from  the  leaves.  Most  of  these  were  not  permanently  injured, 
and  those  that  died  were  burned  so  badly  that  the  outer  skin  was  broken. 
To  produce  this  effect  upon  a  caterpillar  it  must  be  treated  with  a 
direct  blaze  long  enough  to  cause  the  leaves  to  curl  and  blacken  on  the 
plants. 

"Meadow  moths  (Crambus)  flying  about  in  the  grass  were  singed  with 
the  flame.  Some  of  these  would  fly  through  the  flame  so  close  to  the 
burner  that  the  hair  on  one's  hand  would  be  quickly  singed  off.  but  they 


1903]      INSECTICIDE  USE  OF  THE  GASOLINE  BLAST  LAMP.        153 

were  usually  uninjured  by  this  experience.  To  kill  one  of  these  moths 
it  had  to  be  followed  with  the  flame  until  some  parts  were  burned  suf- 
ficiently to  cause  it  to  fall,  when  it  could,  of  course,  be  easily  disposed  of. 

"Lilac  leaves  badly  infested  with  mildew  were  thoroughly  treated, 
the  burner  being  held  at  varying  distances  and  acting  for  varying  periods 
of  time.  The  mildew  does  not  seem  to  have  been  affected  where  the 
leaves  were  not  injured,  and  was  rarely  affected  where  the  leaves 
were  burned  sufficiently  to  cause  them  to  curl  and  later  to  wither. 
Leaves  that  were  treated  to  the  flame  for  three  seconds  dropped  off. 
Other  leaves  treated  one  second  remained  on  the  bush  and  were  not 
perceptibly  injured.  Between  these  two  times  (which  really  represent 
flashing  the  burner  over  the  surface,  and  holding  it  there  for  an  instant) 
the  leaves  showed  varying  injuries.  At  first  the  mildew  appeared  to  have 
been  burned  off,  but  specimens  which  had  been  thoroughly  treated  and 
left  in  the  insectary,  were  again  covered  with  the  mildew  in  five  days. 

"Elm,  Osage  orange,  box-elder,  apple,  cherry,  plum,  grasses,  nastur- 
tiums, cabbage,  pine,  cedar,  Amorpha,  walnut,  rose-bushes,  peach,  and 
several  other  trees  and  ornamental  shrubs  have  been  treated  at  various 
times.  I  find  that  when  the  flame  is  held  close  to  the  foliage  for  a  few 
seconds  this  is  visibly  injured.  If  held  a  short  distance  away  the  injury 
is  not  so  great,  but  usually  shows  after  a  few  days  by  the  blackening  of 
the  leaf  or  by  the  browning  and  curling  of  the  edges.  Often  leaves  so 
treated  will  drop  off. 

"To  sum  up :  The  use  of  sufficient  heat  to  destroy  effectually  insect 
larvae  of  the  kinds  we  treated,  will  injure  the  foliage  and  often  the  twigs." 

Final  mention  may  be  made  of  a  trial  of  the  torch  by  Mr.  Mally,  in 
Ohio,  in  1898,  the  details  of  which  can  not  now  be  given  because  the 
record  is  not  accessible.  This  torch,  obtained  from  Illinois,  was  put  into 
Mr.  Mally's  hands  by  Professor  F.  M.  Webster,  with  instructions  to  give 
it  a  thorough  test.  It  was  taken  by  Mr.  Mally  on  one  of  his  field  trips, 
used  on  a  variety  of  insects,  including  the  chinch-bug,  and  returned  with 
the  general  report  that  it  was  unsatisfactory  for  its  purpose. 

Professors  Webster  and  Pettit  agree  in  a  statement  of  its  usefulness 
rind  convenience  for  "thawing  out  frozen  water  pipes." 

CONCLUSION. — Notwithstanding  the  generally  unfavorable  character 
of  the  statements  made  to  me  concerning  this  torch  by  those  best  able 
to  judge  of  its  value,  it  seems  to  me  that  it  may  have  a  limited  field  of 
usefulness  secondary  to  other  measures  for  the  destruction  of  certain 
kinds  of  injurious  insects.  One  such  use  has  already  been  suggested 
in  the  preceding  paragraphs  on  the  San  Jose  scale.  It  should  certainly 
be  tried  for  such  bugs  (Hemiptera)  as  can  be  lured  away  from  valuable 
crops  to  so-called  trap  crops  of  worthless  plants.  It  might  profitably  be 
tried  in  comparison  with  other  adjuncts  of  the  trap  and  barrier  method 
•for  the  destruction  of  chinch-bugs  as  they  come  out  of  small  grain  for 


154  BULLETIN  NO.  89.  [November.  1903 

their  midsummer  invasion  of  fields  of  corn.  Exact  experiments  should 
be  made  on  the  after  effects  of  brief  exposure  to  its  flame,  as  reported 
by  Professor  Stedman  for  the  harlequin  cabbage-bug,  and  by  Mr.  Titus 
for  the  fall  web- worm  and  other  caterpillars. 

It  should  be  remembered,  however,  that  it  is  probably  the  most  dan- 
gerous to  vegetation  of  any  insecticide  apparatus  which  has  ever  been 
brought  forward  for  common  use,  and  it  consequently  should  not  be 
generally  recommended  for  use  on  living  plants  of  any  value  until 
it  has  been  so  thoroughly  tested  under  various  conditions  that  a  safe 
method  may  be  described  in  terms  which  cannot  be  misunder- 
stood or  misapplied  by  any  ordinarily  intelligent  and  reasonably  careful 
workman. 

Thanks  are  due  to  the  various  gentlemen  who  have  kindly  communi- 
cated their  observations  for  my  use,  and  also  to  Professor  M.  V.  Slinger- 
land,  of  Cornell  University,  who  obtained  for  me  the  information  above 
reported  concerning  a  test  of  the  torch  made  in  New  York  by  Pro- 
fessor Craig. 


UNIVERSITY  OF  ILLINOIS-URBANA 


